The following prior art patent documents are made of record: U.S. Pat. Nos. 4,005,538; 4,200,875; 4,634,220; 4,645,301; 4,650,283; 4,688,894; 4,691,993; 4,708,920; 4,972,061; 5,122,902; 5,151,572; 5,169,707; 5,213,872; 5,542,202; 5,620,613; 5,815,292; 5,885,677; 5,940,212; 5,962,109; 6,010,770; 6,153,128; 6,155,689; 6,217,175; 6,288,842; 6,484,637; 6,644,818; 6,767,609; 6,786,513; 7,033,677; 7,034,688; 7,445,347; Publication No. US2002/0034608; Publication No. US2005/0258637; Publication No. US2008/0092418; Publication No. US/20080212181; EP Patent 1477368; and UK Patent Application 2433637.
It is known to provide a retroflective article having a protective layer over a prismatic film having cube corner prismatic elements, wherein the prismatic elements are coated with an opaque, vapor-deposited, aluminum coating. The aluminum coating is backed by a pressure sensitive adhesive layer which is backed by an interleaf such as an acrylic or polyester layer. A coating of a permanent type adhesive is adhered to the underside of the interleaf layer, and a release liner is adhered to the underlying permanent type adhesive. The underside of the protective layer may be preprinted with a repeating pattern such as a brick pattern, with a zone of pre-printing, such as with clear colored ink, and with reverse printing at the clear color printed zone. While the preprinting, the preprinted zone and the reverse printing at the printed zone are visible against the prismatic retroflective film, the amount of contrast between the preprinting and the prismatic film was limited.
The reverse printing was a logo and/or text such as one indicating the source of the product. This reverse printing provided excellent contrast but had the limitation that only large amounts of material could be preprinted economically. Changes in design were also expensive and could not be done expediently.
What is needed therefore is an improved retroreflective article with having an image with an improved contrast and one which can be provided in an efficient and cost effective manner.